Household and Structural

SPIDERS

Spiders are familiar to everyone. They are closely related
to ticks, mites, and daddy longlegs, all of which have eight
legs and two body regions. Insects, on the other hand, have
six legs and three body regions.

Some people have the idea that all spiders are poisonous
or dangerous to handle, but this is not true. The only spiders
found in Indiana capable of inflicting serious injury to humans
are the black widow and the brown recluse or “fiddleback”
spider. Neither spider will bite unless disturbed. Spider bites are rare but are often falsely implicated - even by medical professionals.

There are nearly 400 species of spiders in Indiana. They
live almost everywhere, including inside homes and buildings.

Spiders feed entirely upon living insects or animals small
enough for them to catch. They usually lie in wait for their
prey, and many build webs to trap them. The webs are made
of fine silken threads produced by “spinnerets” located near
the end of the spider’s abdomen. The silk is secreted in liquid
form, which hardens when exposed to the air. Spiders use
the silk not only to make webs, but also to line their nests,
construct egg sacs, and make “parachutes” on which some
species travel for great distances.

Spiders reproduce by laying eggs contained in an egg
sac. These sacs are usually ball-shaped and may be carried
by the female wherever she goes. Some species hide their
sacs in the web or tuck them away elsewhere. Egg sacs
frequently contain several hundred eggs.

SPIDERS OF MOST CONCERN

Black Widow Spider

The female black widow is jet black in color and, with its
legs extended, would about cover a penny. The abdomen is
spherical and, in the female only, is marked on the underside
with a red or yellow “hour glass.” There may be a few red
spots also on top of the abdomen.

The poison of the black widow affects the nervous system
of humans. Persons bitten may experience a variety of symptoms,
such as dizziness, blurred vision, breathing difficulty,
nausea and severe pain around the wound. In such instances,
a physician should be contacted immediately.

The black widow lives in undisturbed locations, such as
under rocks and boards, and in and around old buildings. She
is active on her irregular web during the day.

Brown Recluse Spider

The mature brown recluse spider has a body about 3/8
inch long and 3/16 inch wide. The leg span is about the size
of a half dollar. The overall color is light tan to deep reddish
brown. The distinguishing mark is a darker contrasting brown
fiddle-shaped area on the front half of the back. This marking
is why the brown recluse is often referred to as the “fiddleback
spider”.

The bite of this venomous spider can cause serious effects.
It is especially dangerous to children, the elderly, and
to those in poor physical condition. Contrary to some reports,
fatalities from bites of the brown recluse are very rare. Reaction
to the bite varies considerably and depends upon the
amount of venom injected and individual sensitivity to it.

Extreme pain may follow almost immediately after the
bite, or the bite may not be noticed for an hour or more. The
visible sign of recluse poisoning is a small white blister at the
site of the bite. The affected area enlarges, becomes inflamed,
and the tissue is hard to the touch. Eventually the affected
tissue is killed and peels away, leaving a sunken, ulcerating
sore up to the size of a silver dollar.

The healing process is slow, requiring 6-8 weeks; in fact,
skin grafts may be needed for complete recovery from the
ulcerated sore.

It is extremely important, therefore, to get medical attention
as soon as possible. Although no specific antidote
is available, prompt medical treatment can prevent severe
reactions and lessen the long-range effects.

The brown recluse is aptly named because it is a reclusive
animal. It is usually found in barns, sheds, garages, or even
in homes that are dry, littered, and contain a supply of insects
to serve as food. Favorite hiding places seem to be the arms
or legs of garments left hanging undisturbed for some time.
People are sometimes bitten while sleeping in beds that have
been unoccupied for a long period.

The Brown recluse Loxosceles reclusa, next to a quarter. (Photo Credit: John Obermeyer, Purdue University)

Close-up of the 6 eyes and the violin-shaped marking of the brown recluse(Photo credit: John Obermeyer, Purdue University)

SPIDER CONTROL IN AND AROUND HOMES

Most spiders can live for several months without food.
Therefore, controlling the insects upon which they feed is a
very slow control technique.

Sanitation is the most practical method of spider control.
Clean away all webbing with a vacuum cleaner so that eggs
and spiders are picked up and destroyed. Ordinary housecleaning
with a cloth, dust mop, or broom is not effective. Keep
premises free of unneeded, undisturbed clothing, papers, and
other litter. Many spiders may be excluded from the home by
caulking or otherwise eliminating cracks and crevices around
the foundation of the house and around windows and doors.

Chemical control using a long-lasting residual spray
containing a pyrethroid insecticide is effective when applied
around the outside of the home and in undisturbed locations in
the house where spiders are likely to be found. Check labels
of specific insecticide products for active ingredient listings.
Aerosols, mists, or fogs containing synergized pyrethrins or
related synthetic pyrethroids can also be used for control
indoors where residual sprays are not desirable.

Outside areas usually needing attention are porches,
garages, and eaves of the roof. Spiders may also be found
in crawl spaces, basements, and unexcavated areas beneath
the house. All areas where spiders are found should
be treated.

READ AND FOLLOW ALL LABEL INSTRUCTIONS. THIS INCLUDES DIRECTIONS FOR USE, PRECAUTIONARY STATEMENTS (HAZARDS TO HUMANS, DOMESTIC ANIMALS, AND ENDANGERED SPECIES), ENVIRONMENTAL HAZARDS, RATES OF APPLICATION, NUMBER OF APPLICATIONS, REENTRY INTERVALS, HARVEST RESTRICTIONS, STORAGE AND DISPOSAL, AND ANY SPECIFIC WARNINGS AND/OR PRECAUTIONS FOR SAFE HANDLING OF THE PESTICIDE.

July 2017

It is the policy of the Purdue University Cooperative Extension Service that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue University is an Affirmative Action institution. This material may be available in alternative formats.

This work is supported in part by Extension Implementation Grant 2017-70006-27140/ IND011460G4-1013877 from the USDA National Institute of Food and Agriculture.